<p>potassium + water = 2K + 2(H2O)</p>
<p>I thought it was: potassium + water = K + H2O</p>
<p>How are you supposed to know the coefficients of 2 belong in front of K and H2O? I'm kinda bad at chemistry... please help!</p>
<p>Well the reaction in the end wants to produce KOH and H2(Hydrogen Gas)</p>
<p>Therefore K + H20 would not react like that because that would mean that a lone hydogen atom would be part of the product and that doesn’t happens since its Hydrogen is diatomic. I do not know if that makes sense but I hope it helps.</p>
<p>Makes sense. Thanks!</p>
<p>Potassium + Water
K + H20 —> KOH + H2
Balance equation
2K + 2H20 —> 2KOH + H2</p>
<p>Potassium is highest on the reactivity chart, so it displaces H in H20 and combines with the OH</p>
<p>It’s 2KOH and H2 to balance the equation.</p>
<p>I don’t think I really answered your question. That’s just what I think potassium + water will result in, although it’s not the same as your formula. I’m taking the chem SAT II in October, so I hope I’m right, lol.</p>
<p>Yamster, you’re correct.</p>
<p>@IJustWannaBe: That same principle doesn’t work with Mg + O2.</p>
<p>I thought: Mg + O2 –> MgO2</p>
<p>but it’s actually: 2Mg + O2 –> 2MgO</p>
<p>Once again, how did that magical 2 appear in front of Mg? this is frustrating!!</p>
<p>Mg + O2
You’re right that this will be a synthesis reaction. Mg has a +2 charge, and oxygen has a -2 charge, so when they combine and you criss-cross the charges you get MgO, so:</p>
<p>Mg + O2 —> MgO
Since we have 2 oxygens on the left side we balance the right side by saying 2MgO, giving us not only 2 oxygens but 2 magnesiums, but we only have 1 Mg on the left, so we balance again by giving Mg on the left a coefficient of 2:</p>
<p>2Mg + O2 —> 2MgO</p>
<p>Left side:
2 Mg
2 O (written as O2 instead of 2O)</p>
<p>Right side:
2MgO, which is 2 Mg and 2O</p>
<p>Therefore the equation is now balanced.</p>